grabbem88

i was trying to get codes off this 93 z28 i prurchased a week ago,and i have a feeling i bought somebody else's mess.

i wondered why my ses light wouldn't come on so i pulled dash and there were no bulbs!..so i tracked down some pc161's put them in and all lights work,but the ses appears to stay powered on?...i used my jumper wire and nothing...no flashes or anything...fans come on and that's about it..all fuses are in and checked...

i'm sorry when i say this car is a pos,cause every car i bought used like this..with problem after problem is cause the prior neglected it or butchered it to make it a pos for the next victim...

is there another way to check codes?

thanks in advance

shoebox

Yeah, you can check codes with a scanner. You might want to trace the wire that feeds the SES light to see if it is the ECM that is actually causing it to come on.

grabbem88

ok makes sense considering the problems i am having,but is it common for a ses light to stay on and not flash when doing the jumper wire method.

what scan tool are we talking about btw...i want to verify if it's the opti spark or computer or what exactly makes this car just shut off for no reason...and it always starts back up on the first hit...

shoebox

Any OBD-I scanner with 12 pin cable will work. It should at least flash a code 12 when in diagnostic mode.

grabbem88

ok brn/wht wire to ses had a bad contact...so after i fix that i can get codes out

codes are 22 low voltage i replaced the tps and i get 4.94v???
code 23 iat did not replace that and voltage is 4.94v ...could this cause tps to be out?
code 15 low temp i replaced that as well so i need to investigate some more
and code 41..no ignition control circuit...open signal from distributor??..need help on that one

Injuneer

With closed throttle, the TPS voltage has to be between 0.20 - 0.90V. That is mesured between the dark blue wire and the black wire. You should get 5.0V (or close) when measuring between the gray wire and the black wire. With the blades fully open, the TPS voltage, measured on the dark blue signal wire should not exceed 4.90V.

I believe the ECT and the TPS share the same ground wire, back to the PCM. I saw in another post (actually, more than one other post) that you had a green and a yellow wire going to the ECT, and you restored the ECT by grounding the green wire. First, wire should be black, not green, and you don't want to ground it to the chassis. You want the ground to be supplied through the ECM. You need to trace the black wire (or green on your car for some reason) wire back to the ECM and insure continuity. The MAP sensor also uses that same ECM ground source.

DTC 41 indicates a problem on the white wire from the ECM to the IC Module. That's the wire that tells the ICM to fire the coil. You need to measure the voltage on the wire.

http://shbox.com/1/4th_gen_tech2.html#opti_test

grabbem88

tps code and iat code was because i never cleared codes..and as of 41 i goofed on my meter and popped fuse therefore when i cleared codes it cleared as well

then 13 came up after test drive..jacked car up and seen d/s o2 unplugged..(i guess i didn't push it in hard enough...

back to green/blue wire deal...the yellow and black wires are correct..scan tool showed computer requesting fans to be on,but i don't like those temps...so i spliced into the blue and green wire and grounded it from the relay's to the ground strap on frame so i have both fans running with key on and fans off with key off..

thanks for all your help..and i love shbox...helped alot

Injuneer

You complain in another thread that the wiring in your car is all hacked up by the previous owner. Then, rather than reprogram the fan on/off temps, you hack the wiring to cause the fans to run all the time. I don't get it.

grabbem88

every car i have ever owned i solder/shrink tube/wire loom it..you would never have known..besides it's cheaper than running a toggle switch,and having wires everywhere..or that jet performance controller..and you can easily change it back to the old way..snip two wires and it's back to normal..

like i said in other post i'll be away for 2 months and i'd rather know wife/kids won't be stranded on side of road if it does decide to over heat on them..

we all need hobbies and transportation and when it comes to family...it's transportation first

shoebox

Running the fans all the time is way unnecessary (especially both of them). What happens when you really need the fans and they have worn themselves out by constant use? Constant fan operation can also hinder getting the engine up to good operating temperature when it is cold/cool out. Poor combustion, performance, gas mileage and shorter engine life could be the result of operating too cold.

The stock temps in the fan system are perfectly capable of keeping the engine cool (even though some people think it is too hot). Thousands of them are out there in daily use without an issue.

grabbem88

it will be fine for two months of my wife driving it..besides i have two more fans in basement if these two fail..lol when at full temp at idle peak temp was 202*

Injuneer

Did you consider how running a ground loop to the chassis on that wire might affect the voltage reading of the other sensors that use the same wire for the PCM ground, that I mentioned above? The voltage readings are critical to the operation of the engine, and that's why the ground is referenced directly to the PCM, without relying on a chassis ground that may or may not be good.

Chaos1187

For reference as well...your speaking to two of the most knowledgeable people Ive ever met...Who deal specifically with our vehicles.

grabbem88

ok so why did two gm tech's and my buddy who runs a dyno shop which has won pinks and placed 3rd in mustang fast fords in a dyno shoot-out...all tell me it wont hurt a thing?

Chaos1187

Well in the end you do what you want to do. And that would be a question to ask them not anyone here. As I said just for reference...but Id take these guys words over any other mechanic etc.

They helped me bring my "POS" up to standards very quickly and I never touched a Camaro up until the one I have now. Running quit well to date.